The metabolism of deoxyguanosine in mitochondria. Characterization of the uptake process.

The uptake of deoxyguanosine by rat liver mitochondria was characterized. The process required an intact mitochondrial membrane and exhibited a dependence on added phosphate. Deoxyguanosine uptake was minimally influenced by Mg2+ or Mn2+, but Ca2+ at concentrations above 0.5 mM were detrimental. Of the deoxynucleosides tested, only deoxyinosine inhibited the uptake of deoxyguanosine. The ribonucleoside guanosine was not observed to compete with its deoxynucleoside analog. Known inhibitors of nucleoside transport, cytochalasin B and NBMPR, did not block deoxyguanosine uptake, but the sulfhydryl reagents NEM and pCMB were both inhibitory. The uptake of deoxyguanosine was shown to be a saturable process and an apparent Km of 0.64 microM was calculated from a Hanes plot.